* [PATCH] kcov: Don't trace the code coverage code
@ 2016-04-13 16:22 James Morse
2016-04-13 16:27 ` Dmitry Vyukov
0 siblings, 1 reply; 2+ messages in thread
From: James Morse @ 2016-04-13 16:22 UTC (permalink / raw)
To: linux-kernel
Cc: Dmitry Vyukov, Andrew Morton, Alexander Potapenko, James Morse
Kcov causes the compiler to add a call to __sanitizer_cov_trace_pc() in
every basic block. Ftrace patches in a call to _mcount() to each function
it has annotated.
Letting these mechanisms annotate each other is a bad thing. Break the
loop by adding 'notrace' to __sanitizer_cov_trace_pc() so that ftrace
won't try to patch this code.
Signed-off-by: James Morse <james.morse@arm.com>
---
This patch lets arm64 with KCOV and STACK_TRACER boot.
kernel/kcov.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/kcov.c b/kernel/kcov.c
index 3efbee0834a8..78bed7125515 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c
@@ -43,7 +43,7 @@ struct kcov {
* Entry point from instrumented code.
* This is called once per basic-block/edge.
*/
-void __sanitizer_cov_trace_pc(void)
+void notrace __sanitizer_cov_trace_pc(void)
{
struct task_struct *t;
enum kcov_mode mode;
--
2.8.0.rc3
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] kcov: Don't trace the code coverage code
2016-04-13 16:22 [PATCH] kcov: Don't trace the code coverage code James Morse
@ 2016-04-13 16:27 ` Dmitry Vyukov
0 siblings, 0 replies; 2+ messages in thread
From: Dmitry Vyukov @ 2016-04-13 16:27 UTC (permalink / raw)
To: James Morse; +Cc: LKML, Andrew Morton, Alexander Potapenko
On Wed, Apr 13, 2016 at 6:22 PM, James Morse <james.morse@arm.com> wrote:
> Kcov causes the compiler to add a call to __sanitizer_cov_trace_pc() in
> every basic block. Ftrace patches in a call to _mcount() to each function
> it has annotated.
>
> Letting these mechanisms annotate each other is a bad thing. Break the
> loop by adding 'notrace' to __sanitizer_cov_trace_pc() so that ftrace
> won't try to patch this code.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
> This patch lets arm64 with KCOV and STACK_TRACER boot.
>
> kernel/kcov.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 3efbee0834a8..78bed7125515 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -43,7 +43,7 @@ struct kcov {
> * Entry point from instrumented code.
> * This is called once per basic-block/edge.
> */
> -void __sanitizer_cov_trace_pc(void)
> +void notrace __sanitizer_cov_trace_pc(void)
> {
> struct task_struct *t;
> enum kcov_mode mode;
> --
> 2.8.0.rc3
Thanks!
Acked-by: Dmitry Vyukov <dvyukov@google.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2016-04-13 16:22 [PATCH] kcov: Don't trace the code coverage code James Morse
2016-04-13 16:27 ` Dmitry Vyukov
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